Plain carbon steel hub for data storage device

ABSTRACT

A rotating removable data storage device hub, such as a hub for a micro-floppy magnetic data storage disc, that has a core of plain carbon steel and a primary coating. The hub may also include a vapor corrosion inhibiting layer on the primary coating. The plain carbon steel can have about 0.5% or less carbon. The primary coating can be tin, nickel, zinc, chrome, paints, epoxies, epoxy-urethanes, phenolic resins, and combinations thereof. The vapor corrosion inhibiting layer may include an amine to reduce the rate of oxidation of the plain carbon steel core.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/692,942 filed on Aug. 7, 1996 abandoned.

FIELD OF THE INVENTION

The present invention relates to the field of data storage devices. Moreparticularly, the present invention relates to plain carbon steel hubsfor rotating removable data storage devices.

BACKGROUND OF THE INVENTION

Typical removable data storage devices rely on rotation of the datastorage media about a hub to record and read data. Examples of suchremovable devices include magnetic data storage discs, magnetic datastorage tape cartridges, and magneto-optical discs.

Removable magnetic data storage discs typically include a polyesterresin or the like having a magnetic layer on each side thereof on whichinformation is recorded by a magnetic head. Flexible magnetic datastorage discs which have a diameter of 31/2 inches (90 mm) or less areknown as micro-floppy discs and will be referred to so herein.Generally, the micro-floppy disc is accommodated in a hard casing toform a cartridge.

The flexible magnetic data storage disc comprises a thin circularmagnetic recording medium having a hub at its center. The hub serves asa means of rotating the recording media over recording heads. Typicalhubs are made of AISI/SAE 430/431 Stainless Steel because of itsdurability, corrosion resistance, and susceptibility to magneticattraction. Some hubs are provided in uncoated stainless steel, whileothers have been coated with chrome or epoxy to enhance their appearanceor wear properties.

The disc hub plays an important role in proper operation of the disc.FIG. 1 is an exploded view of a typical micro-floppy disc drive spindle10 and hub 20, including an annular ring of magnetic media 21 attachedto the hub 20. The drive spindle 10 includes a center pin 12 andalignment pin 14 that is spring-loaded to be biased away from the centerpin 12. The center pin 12 is received in the center pin opening 22 ofthe hub 20 while the alignment pin is received in the alignment window24.

FIG. 2 is a top view of the hub 20 properly mounted on a drive spindle10 in which the center pin 12 of the drive 10 is received in the centerpin opening 22 and the alignment pin 14 is properly located in thealignment window 24. As shown, the alignment pin 14 is urged towards thecenter pin 12 during rotation of the hub 20 (and attached recordingmedia--not shown) by the window 24. The drive spindle 10 is typicallymagnetized to attract the hub 20 towards the drive 10 during loading anduse of the disc. Although proper seating and orientation of the hub onthe drive typically occurs without fault, there are a number of errorswhich can occur that cause errors in the writing or reading of data fromthe media.

FIG. 3 depicts one error that can occur in seating of the hub 20 ondrive spindle 10. This error involves failure of the alignment pin 14 toproperly seat in the alignment window 24 in hub 20. As shown, thealignment pin 14 has only moved partially towards its proper position inthe comer of the window 24. This error prevents proper positioning ofthe recording media relative to the read/write heads in the disc drive.Errors of the this type are typically detected with a test commonlyreferred to as "Index to Data."

FIGS. 4 and 5 depict another error in seating of the hub 20 on the drivespindle 10. This error, referred to as a "mischuck," results in liftingof the hub 20 off of the drive spindle 10 in the area of the alignmentpin 14. As a result, the hub 20 is canted on the drive spindle 10 andproper alignment of the media with respect to the read/write heads inthe disc drive cannot be maintained. That improper alignment typicallyresults in modulation errors as data is read from and written to thedisc.

Similar concerns can plague manufacturers and users of other rotatingremovable data storage devices that incorporate a hub that mates with aspindle to rotate the data storage media, whether that media stores datamagnetically or optically. Examples of such devices include removablemagnetic data storage discs other than micro-floppy discs, removablemagnetic data storage tape cartridges, and magneto-optical data storagediscs.

Although the errors discussed above occur infrequently and are typicallytested for by manufacturers of high quality removable data storagedevices, any improvements that further reduce their incidence can beextremely valuable in terms of improved manufacturing yields in additionto increasing the reliability of the devices in use by purchasers.

SUMMARY OF THE INVENTION

The present invention provides a rotating removable data storage devicehaving a hub of coated plain carbon steel. By using plain carbon steelfor the hub a number of advantages are achieved by the presentinvention. The magnetic force generated between the drive spindle andthe hub is typically increased, resulting in fewer mischucks. Also, thecost of the hubs is reduced because of the substitution of plain carbonsteel for the stainless steel typically used. A coating over the plaincarbon steel resists corrosion of the plain carbon steel hub and mayalso assist in preventing improper seating of the hub on the drivespindle. Additional vapor corrosion inhibiting layers may also improvethe corrosion resistance for the coated plain carbon steel hubs.

In one aspect, the present invention provides a hub for a rotatingremovable data storage device having a core of plain carbon steel and acoating on at least a portion of the core. Preferably, the plain carbonsteel comprises about 0.5% or less carbon, more preferably about 0.2% orless carbon. Some preferred coatings can be selected from the groupconsisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof.

One hub according to the present invention is provided in a microfloppymagnetic data storage disc.

In another aspect, the present invention comprises a micro-floppymagnetic data storage disc having a hub with a core of plain carbonsteel and a coating on at least a portion of the hub. Preferably, theplain carbon steel comprises about 0.5% or less carbon, more preferablyabout 0.2% or less carbon. Some preferred coatings can be selected fromthe group consisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof.

In another aspect, the present invention comprises a hub for a rotatingremovable data storage device including a core comprising plain carbonsteel; a primary coating on at least a portion of the core; and a vaporcorrosion inhibiting layer on the primary coating. The vapor corrosioninhibiting layer may be an amine.

In another aspect, the present invention comprises a method ofmanufacturing a hub for a rotating removable data storage devicecomprising steps of forming a core of plain carbon steel; providing aprimary coating on the core; and providing a vapor corrosion inhibitinglayer on the primary coating. The step of providing the vapor corrosioninhibiting layer may include depositing the layer by aqueous solution,in vapor phase, or a combination of an aqueous solution and vapor phasedeposition.

These and other features and advantages will be described in more detailbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of the interface between a microfloppy huband drive spindle.

FIG. 2 is a plan view of a micro-floppy disc hub properly seated on adrive spindle.

FIG. 3 is a plan view of a micro-floppy disc hub improperly seated on adrive spindle that typically results in an index to data error.

FIG. 4 is a plan view of a micro-floppy disc hub improperly seated on adrive spindle due to a mischuck that typically results in a modulationerror.

FIG. 5 is a side view of the micro-floppy disc hub and drive spindle ofFIG. 4.

FIG. 6 is a perspective view of one micro-floppy disc hub according tothe present invention.

FIG. 7 is an enlarged partial cross-sectional view of the hub of FIG. 6.

FIG. 8 is a graph of the intensity of magnetization as a function ofmagnetic field strength for AISI/SAE 1008 Cold-Rolled Steel and 430Stainless Steel.

FIG. 9 is an enlarged cross-sectional view of a portion of a hubmanufactured according to the present invention.

FIG. 10 is a perspective view of the hub of FIG. 9.

FIG. 11 is an enlarged cross-sectional view of a portion of the hub ofFIG. 9 including a vapor corrosion inhibiting layer.

FIG. 12 is a graph of the results of corrosion testing of materials usedto manufacture hubs according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a hub for rotating removable data storagedevices that can reduce error in positioning the hub on a drive spindleby using a coated plain carbon steel hub that exhibits improved magneticproperties, resists corrosion and reduces the cost of manufacturing thehub. Although the following discussion focuses generally on hubs formicro-floppy magnetic data storage discs, it will be understood that thehubs according to the present invention may find use in connection withany rotating removable data storage device having a hub, whether thatdata is stored magnetically, optically, or in any other manner. Examplesof such devices include, but are not limited to: any removable magneticdata storage disc, removable magnetic data storage tape cartridges,removable magneto-optical data storage discs, and digital video discsthat may include a metallic hub.

FIGS. 1-5 described above depict the interface between a micro-floppydisc hub 20 and drive spindle 10. The design of the micro-floppy disc issubject to American National Standards Institute (ANSI) Standardx3.171-1989 and equivalents which are hereby incorporated by reference(equivalents include ISO/IEC 9529-1:1989 and European ComputerManufacturers Association ECMA/TC19/87/21) to allow interchangeable useof discs in different disc drives, both of which may be manufactured bymany different companies. As a result, the dimensions of the hubs forsuch discs do not typically vary significantly between manufacturers. Asdescribed above, the typical hubs 20 are manufactured of stainless steelbecause of its durability and corrosion resistance. The stainless steelhubs are typically stamped from sheet stock to the desired shape.

The drive spindles 10 are typically remanently magnetized or includemagnets in their construction to provide a magnetic attraction betweenthe spindle and hub that tends to draw the hub against the spindle.Magnetic fields measured near the magnetic poles on commerciallyavailable drive spindles range from about 290 to about 550 Oe, with anaverage of about 400 Oe. These measurements were taken using acommercially available gaussmeter located near the poles of the magnetsin the drive spindles.

FIG. 6 depicts a micro-floppy disc hub 120 including center pin opening122 and alignment window 124. The hub can be manufactured by anysuitable method, although typically the hub 120 will be manufactured bystamping procedures as are known stainless steel micro-floppy disc hubs.As seen in FIG. 7, the hub 120 includes a core 126 of plain carbon steeland a coating 128 over the core 126.

The core preferably comprises a plain carbon steel. As used herein, theterm "plain carbon steel" does not include steels with significantalloying components (such as stainless steels). Preferably, plain carbonsteels according to the present invention have about 0.5% carbon contentor less (although it will be understood that the plain carbon steelsmust include at least some carbon). More preferably, hubs according tothe present invention are manufactured with plain carbon steel havingabout 0.2% carbon content or less. Examples of suitable steels include,but are not limited to: AISI/SAE 1008, 1010, 1018 and 1020 steels. It isalso preferred that the hubs be formed of cold-rolled plain carbon steelbecause of its strength and hardness.

The plain carbon steel exhibits improved magnetic properties overstainless steel. Although both materials are magnetically soft (withcoercivities of about 12 Oe for AISI/SAE 430 Stainless Steel and about 8Oe for AISI/SAE 1008 Cold-Rolled Steel), the plain carbon steel exhibitsincreased intensity of magnetization as compared to AISI/SAE 430Stainless Steel. These properties can be measured using avibrating-sample magnetometer. Two typical intensity of magnetizationcurves for AISI/SAE 1008 Cold-Rolled Steel and 430 Stainless Steel arepresented in FIG. 8.

Because of the increased intensity of magnetization, a hub manufacturedfrom plain carbon steel will exhibit greater magnetic attraction thanwill a similar hub manufactured from stainless steel. Typical stainlesssteel micro-floppy disc hubs of AISI/SAE 430 Stainless Steel with athickness of 0.012 inches (0.305 mm) exhibit a magnetic force ofattraction of about 890 grams-force to a drive spindle with a magneticfield of about 1140 Oe as set forth in Example 1 below. In contrast,hubs 120 manufactured using plain carbon steels with the same thicknesstypically exhibit a magnetic force of attraction to the same drivespindle of about 1000 grams-force or more (i.e., about a 12% or greaterincrease). That additional magnetic attraction force contributes toimproved seating of hubs on the drive spindles, thereby improvingmanufacturing yields in formatting tests and reliable use by consumers.

The increased magnetic clamping force attributed to the plain carbonsteel (as compared to stainless steel) allows for the use of thinnerhubs without significantly degrading the magnetic clamping force neededto assure proper positioning of the hub on a drive spindle. For example,hubs having a thickness of about 0.0095 inches (0.241 mm) or lesstypically exhibit a magnetic clamping force approximately equivalent toa thicker stainless steel hub as set forth in Example 2 below. Thisoccurs because the increased intensity of magnetization of the plaincarbon steel provides a larger magnetic attractive force for the sameamount of material as compared to stainless steel (See FIG. 8). Thethinner hubs provide further cost advantages for discs with plain carbonsteel hubs due to reduced material costs.

Corrosion of plain carbon steels is a greater concern than with typicalstainless steel hubs and the coating 128 on core 126 assists inresisting corrosion. Suitable coatings will exhibit the desired wearresistance and durability needed for micro-floppy discs that areinserted into and removed from disc drives numerous times over theiruseful life. The coating 128 may be provided over the entire hub 120 orover portions thereof. For example, it may be necessary to provide thecoating only over those portions the hub 120 that contact the drivespindle.

Examples of suitable coatings 128 include metals and paints. Somedesirable metallic coatings include tin, nickel, zinc, and chrome.Typically, the metallic coatings 128 will be electro-plated onto theplain carbon steel core 126, either before the hubs 120 are formed or,alternatively, after the hub 120 has been formed. The metallic coatingscan have either bright or matte finishes.

One preferred hub 120 includes a coating 128 of tin (7C Brite Finish)with a thickness of about 15 microinches (0.38 micrometers) on a core126 of AISI/SAE 1008 cold-rolled plain carbon steel. The thickness ofthe hub 120 including plating is about 0.0120 inches (0.305 mm) Suitablematerial having these specifications is available from U.S. Can MetalServices Company (Chicago, Ill.). The desired plated cold-rolled steelhas a 7C Brite finish.

Some examples of suitable paints for coating 128 include organic paints,enamels, lacquers, plastic dip coatings, epoxies, epoxy-urethanes,phenolic resins, etc. These materials can be applied by spray coating,roll coating, dip coating, or any other suitable process.

Although only one coating 128 will typically be applied to the core 126,it will be understood that two or more coatings may be applied. Thesecoatings may be applied over other coatings, i.e., a multi-layercoating, or on different coating on the side 121 (See FIG. 6) of the hub120 that is hidden from view in a typical micro-floppy disc. The primarypurpose for the coating 128 on that side of the hub 120 is to resistcorrosion of the plain carbon steel core 126. The side 123 of the hub120 that is exposed during handling and use could be coated with adifferent coating that enhances appearance, wear resistance, corrosionresistance or a number of other factors. One particularly helpfulcombination of coatings may include a coating of nickel on side 123 anda less-expensive coating such as tin, zinc, paint, etc. on side 121 ofmicro-floppy hub 120.

Referring to FIG. 9, an enlarged cross-section of a hub 220 is depictedwhich includes a core 226 of plain carbon steel as discussed above. Thecore 226 is coated with a primary coating 228 to enhance corrosionresistance, wear or any other desired properties. Typically, however,the hub 220 will be coated with a metallic primary coating or a paintsuch as those described above. One potential problem with such primarycoatings, however, is their susceptibility to cracking, crazing andother surface defects 230 depicted in FIG. 9. Defects 230 can expose theplain carbon steel core 226 to ambient moisture and those exposed areas232 of the core 226 may be corroded, thereby degrading the appearanceand potentially affecting performance of the hub 220. It is important tonote that the size of the defects 230 may be relatively small and maynot typically be noticed by a user. The corrosion that may begin in thedefects 230 could, however, enlarge the defect 230 and/or cause partialdelamination of the primary coating 228 from the core 226, therebymaking the defect 230 more visible over time.

As used in connection with the present invention, "corrosion" will refereither only to oxidation or, at least primarily, to oxidation of theplain carbon steel core. The oxidation rate of the exposed portions ofthe ferrous plain carbon steel core is increased by ambient moisture.The vapor corrosion inhibiting layer of the present invention willreduce the rate of oxidation and, in some cases, may effectivelyeliminate the corrosion when viewed in light of the useful life of therotating removable data storage devices incorporating these hubs.

The defects 230 in the primary coating 228 may have a number of causes,but one typical cause with metallic plated hubs such as hub 220 isduring stamping of the hub 220 from a larger sheet of plated carbonsteel. Stamping hubs from preplated sheets of plain carbon steel is oneeconomical method of manufacturing the hubs. One potential disadvantage,however, is the creation of surface defects 230 in hubs 220 duringstamping, particularly in the areas being deformed such as around thecenter pin opening 222 (see FIG. 10). Other areas susceptible to surfacedefects during stamping include the shoulder 234 and flange 236 formedaround the edge of the hub 220. Similar problems would be expected ifthe primary coating 228 were a paint, epoxy, or other non-metalliccoating applied to the sheets of plain carbon steel before the hubs 220were stamped.

In addition to stamping, however, the surface defects 230 may also occuras a result of a substandard plating or coating process that results invoids or pinholes in the primary coating. These defects could occur evenif the hubs 220 were coated after stamping.

Corrosion at surface defects in hubs according to the present inventioncan, however, be reduced if a vapor corrosion inhibiting layer 238 isapplied to the hubs 220 over the primary coating 228. The vaporcorrosion inhibitor can prevent ambient moisture vapor from contactingthe exposed areas of the core 226 in the areas of surface defects 230 asseen in FIG. 11 by forming a generally conformal layer 238 of a vaporcorrosion inhibiting material that can be deposited in the surfacedefects 230 to protect the core 226 as well as on the primary coating228.

The materials used for the vapor corrosion inhibiting layer 238 arepreferably capable of inhibiting both anodic and cathodic attack uponthe plain carbon steels used for the core 226 of hubs 220 according tothe present invention. It is preferred that the vapor corrosioninhibiting layer 238 include one or more amines in addition to othercomponents such film formers, surfactants, waxes, etc. Representativeexamples of such coatings and methods of providing them are described,for example, in U.S. Pat. Nos. 4,051,066; 4,275,835; 5,139,700;5,209,869; 5,320,778; 5,344,589; 5,332,525; 5,393,457; and 5,422,187;which are hereby incorporated by reference.

The thickness of vapor corrosion inhibiting layer 238 may vary, althoughthe nominal thickness of the layer 238 is preferably about 30 to about40 Å (as measured by Ion Scattering Spectroscopy (ISS) or Secondary IonMass Spectroscopy (SIMS)). It is preferred that the vapor corrosioninhibiting layer 238 be thin enough to avoid detection by the ordinaryuser, i.e., the layer 238 should not be visible to the naked eye norshould it be particularly noticeable during handling of the hubs 220during normal use. In other words, the layer 238 should not cause thehubs 220 to appear or feel oily or greasy in normal use.

The vapor corrosion inhibiting layer 238 could be applied by a number ofmethods including liquid immersion/spraying, vapor phase deposition, ora combination of both liquid immersion/spraying and vapor phasedeposition.

In one preferred vapor phase deposition process, the amine corrosioninhibitors used for layer 238 are preferably deposited in a passivevapor deposition process in which the hubs 220 are placed in enclosuresin which the corrosion inhibitor is located in a desiccant, anothercarrier, or in the packaging materials themselves as recited in a numberof the patents listed above. Because the corrosion inhibitors vaporizeunder standard atmospheric conditions, they are deposited in vaporphase, on the surface of the hubs 220 during the time the hubs arepresent in the enclosure. It is preferred that the vapor phasedeposition process be carried out for at least 24 hours to ensureadequate vapor phase deposition.

In one preferred liquid deposition process, the hubs can be immersed inan solution containing the vapor corrosion inhibiting materials(preferably one or more amines) after which they are dried. The solutionmay also include other components such as surfactants, film formers,waxes, etc. to assist in forming the vapor corrosion inhibiting layer238.

Where the hubs including a vapor corrosion inhibiting layer are to beused in magnetic data storage devices such as micro-floppy discs, it ispreferred that the magnetic media be attached to the hub after the vaporcorrosion inhibiting layer is in place to avoid exposing and/or coatingthe media with the vapor corrosion inhibiting layer.

Tests performed on some representative plated steels that can be usedfor hubs according to the present invention show significantimprovements in resistance to corrosion. Some test results are depictedgraphically in FIG. 12 and the test methods used to achieve thoseresults are described in Example 4 below. Briefly, however, the hubs 220including a vapor corrosion inhibiting layer 238 show significantimprovements in corrosion resistance.

EXAMPLES

Features and advantages of the coated plain carbon steel micro-floppydisc hubs according to the present invention are further illustrated inthe examples. It is recognized, however, that while the examples servethis purpose, the particular plain carbon steels and coating used, aswell as other conditions and details, are not to be construed in amanner that would unduly limit the scope of this invention. Thefollowing tests were used to evaluate plain carbon steel micro-floppydisc hubs of the present invention.

MAGNETIC CLAMPING FORCE TEST

Micro-floppy disc hubs manufactured with the dimensions set forth inANSI x3.171:1989 were mounted on an Optical Hub Pushoff Tester (ModelNTS4700A, Kato Spring Works Co. Ltd., Japan (Ser. No. 910613-2)). Thedrive spindle incorporated in this machine had a magnetic field measurednear its magnetic poles of about 1140 Oe as measured with a hand-heldgaussmeter located near the poles of the magnets in the spindle.

To determnine the magnetic clamping force, the hubs were placed on thetest spindle (subject to the magnetic attractive force) and the spindlewas automatically lowered at a constant rate. During movement of thespindle, the movement of the hub is restrained by a retaining ring suchthat the spindle pulls away from the hub (as restrained by the retainingring). As the spindle moves away from the hub, the maximum magneticclamping force is recorded by a load cell attached to the spindle,thereby providing the maximum magnetic clamping force as used inconnection with the present invention.

Example 1

Micro-floppy disc hubs were manufactured by stamping from sheet stockwith a nominal thickness of about 0.012 inches (0.305 mm) according tothe dimensions set forth in ANSI x3.171:1989. Table 1 lists the variousmaterials used for the core and coating (if any) along with the MagneticClamping Force as measured according to the test described above (usinga spindle having a magnetic field measured near its magnetic poles ofabout 1140 Oe as measured with a handheld gaussmeter located near thepoles of the magnets in the spindle).

The AISI/SAE 430 Stainless Steel used for the tested hubs was purchasedfrom Allegheny Ludlum Steel, Wallingford, Conn. The epoxy used to coatsome of the 430 Stainless Steel hubs was an epoxy-urethane.

The material for the hubs manufactured of AISI/SAE 1008 steel werepurchased from U.S. Can Metal Services (Chicago, Ill.) as 1008 ColdRolled Steel, 0.0118±0.0006 inches thick (107 pound/base box ±5% or300±3.2 micrometers), T5 Temper (30T scale). The pre-plated (i.e.,plated before stamping the hubs) tin coating was 0.25 pound/base boxBrite 7C Tin Plate (0.11 pound/base box minimum per side). The matte tincoating was a No. 5 matte tin finish and the nickel was electrolesspost-plated (i.e., plated after stamping) using Watts Brite nickel.

                  TABLE 1    ______________________________________                               Clamping                      Coating  Force    Core              Thickness                               (grams- Std. No. of    Material            Coating   (μm)  force)  Dev. Tests    ______________________________________    430 Stainless            None      --        889    8.6  20    Steel    430 Stainless            Chrome    3.81      855    3     2    Steel    430 Stainless            Epoxy     1.91      802    36.4 10    Steel    1008 Steel            None      --       1024    23.6 20    Same    Matte Tin 0.381    1005    26.3 30    Same    Brite Tin 0.381    1022    17    7    Same    Nickel    2.29     1058    11.2 10    ______________________________________

Example 2

Micro-floppy disc hubs were manufactured by stamping from sheet stockaccording to the dimensions set forth in ANSI x3.171:1989 with theexception that the sheet stock had a nominal thickness of about 0.0095inches (0.241 mm). Table 2 lists the various materials used for the coreand coating (if any) along with the Magnetic Clamping Force as measuredaccording to the test described above.

                  TABLE 2    ______________________________________                               Clamping                      Coating  Force    Core              Thickness                               (grams- Std. No. of    Material            Coating   (μm)  force)  Dev. Tests    ______________________________________    430 Stainless            None      --       736      8.6 10    Steel    1008 Steel            Brite Tin 0.381    878     22.0 12    ______________________________________

Example 3

Micro-floppy disc hubs were manufactured by stamping from sheet stockaccording to the dimensions set forth in ANSI x3.171:1989 with theexception that the sheet stock had a nominal thickness of about 0.0080inches (0.203 mm). Table 3 lists the various materials used for the coreand coating (if any) along with the Magnetic Clamping Force as measuredaccording to the test described above.

                  TABLE 3    ______________________________________                               Clamping                      Coating  Force    Core              Thickness                               (grams- Std. No. of    Material            Coating   (μm)  force)  Dev. Tests    ______________________________________    430 Stainless            None      --       649     19.5 10    Steel    1008 Cold-            Brite Tin 0.381    813      7.6  4    Rolled Steel    ______________________________________

Example 4

Micro-floppy disc hubs were manufactured by stamping from sheet stockwith a nominal thickness of about 0.012 inches (0.305 mm) according tothe dimensions set forth in ANSI x3.171:1989. The sheet stock wasAISI/SAE 1008 steel purchased from U.S. Can Metal Services (Chicago,Ill.) as 1008 Cold Rolled Steel, 0.0118±0.0006 inches thick (107pound/base box ±5% or 300±3.2 micrometers), T5 Temper (30T scale). Thesheet stock was pre-plated (i.e., plated before stamping the hubs) witha tin coating, specified as 0.25 pound/base box Brite 7C Tin Plate (0.11pound/base box minimum per side).

Some of the hubs were retained as controls (i.e., not treated with avapor corrosion inhibitor), while others were treated with a corrosioninhibitor according to the following methods.

Group 1:

A first group of hubs (designated Group 1) were prepared by liquidimmersion and vapor phase deposition of vapor corrosion inhibiting layeras follows.

Aqueous solutions of a vapor corrosion inhibitor (VCI) material wereprovided in concentrations ranging from 0.5% to 2% (by weight). Thevapor corrosion inhibitor was VCI-379 purchased from Cortec Corporation,White Bear Lake, Minn. In addition to the amine vapor corrosioninhibitor, the VCI-379 also includes suitable film formers, surfactants,waxes, and other components required to assist in depositing a vaporcorrosion inhibiting layer including an amine.

Freshly stamped hubs as described above were cleaned by aqueous washingin which the hubs were immersed in a high pH (about 8.5 to about 10)aqueous detergent solution that was heated to 140±5° F. (60±3° C.). Thehubs were agitated in the detergent solution for 2-4 minutes after whichthe hubs were immersed in a heated rinse water tank (140±5° F. or 60±3°C.) and agitated for 2-4 minutes. Alternatively, the hubs could becleaned in a heated solution of trichloroethylene.

The cleaned hubs were then immersed and agitated for 1-3 minutes in theaqueous solution including the vapor corrosion inhibitor material. Afterbeing removed from the vapor corrosion inhibitor solution, the hubs wereair dried in an oven at 210±10° F. (99±5° C.) for 15-20 minutes afterwhich they were allowed to cool to room temperature.

The hubs were then tested. The results of tests on this group of hubs isdepicted in Table 4 below as Group 1 along with the variables used indeveloping the Eyring Acceleration Model used to arrive at the expectedsurvival rate.

Group 2:

A second group of the hubs (designated as Group 2) was subjected only tovapor phase deposition of the vapor corrosion inhibitor as discussedbelow.

Freshly stamped hubs as described above were cleaned by aqueous washingas described above for Group 1. The cleaned hubs were then dried andplaced in plastic bags formed with a vapor corrosion inhibitor in thepackaging material. The material used for the bags was VCI-126,available from Cortec Corporation. Also inserted into each bag was avapor phase emitter containing an active amine that vaporizes atstandard atmospheric conditions. The vapor phase emitter pouches usedwere designated 1-MUL, also available from Cortec Corporation.

The hubs were retained in the bags for at least 24 hours after whichthey were removed for environmental testing. The results of tests onthis group of hubs is depicted in Table 4 below as Group 2 along withthe variables used in developing the Eyring Acceleration Model used toarrive at the expected survival rate.

Group 3:

A third group of the hubs (designated as Group 3) was maintained as acontrol group. The hubs in the control group were cleaned by aqueouswashing as described above for Group 1. The hubs were then subjected toenvironmental testing. The results of tests on this group of hubs isdepicted in Table 4 below as Group 3 along with the variables used indeveloping the Eyring Acceleration Model used to arrive at the expectedsurvival rate.

                  TABLE 4    ______________________________________    Group  A        ΔH                            B     Scale Shape  Years    ______________________________________    1      -9.3     .72     -10.9 61    1.61   9.6    2      -4.4     .48     -5.5  14    3.44   6.8    3      -17.2    .80     -7.0   4    1.35   0.4    ______________________________________

Corrosion Testing of Groups 1-3

The different groups of hubs prepared as described above were thenplaced in environmental testing chambers and subjected to controlledconditions to collect the data needed to develop an Eyring AccelerationModel for each group.

The tests were conducted by placing the hubs in an environmental testingchamber in which both temperature and humidity could be controlled. Thedata collected was used to develop an Eyring Acceleration Model of theexpected life of representative plain carbon steel hubs having a primarycoating and vapor corrosion inhibiting layer, as well as control groupsof hubs having no additional vapor corrosion inhibiting layer. For thepurposes of the tests, 0.049" (1.24 mm) in any direction on the surfaceof the material was established as the maximum size for a defect withcorrosion, at which point the part was determined to have reach thepoint of failure.

The results of the corrosion testing for conditions of a temperature of25° C. and 50% Relative Humidity are depicted in Table 4 and in FIG. 12.They show the improvements in expected survival of hubs manufacturedwith a vapor corrosion inhibitor according to the present invention. Theresults shown in the years column of Table 4 are the point at which 5%of the hubs can be expected to have developed defects having the size of0.049 inches (1.24 mm). This is also the point at which 95% of the hubscan be expected to have survived, i.e., the surviving hubs would nothave developed defects having a size of 0.049 inches (1.24 mm). FIG. 12is a graphical representation of the results of the Eyring AccelerationModel including a curve 240 for Group 1, curve 242 for Group 2, andcurve 244 for Group 3.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope ofthis invention, and it should be understood that this invention is notto be unduly limited to the illustrative embodiments set forth herein.

What is claimed is:
 1. A hub for a rotating removable data storagedevice comprising:a) a core comprising plain carbon steel having about0.2% or less carbon; and b) a coating on at least a portion of the core.2. The hub of claim 1, wherein the coating is selected from the groupconsisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof.
 3. The hubof claim 1, further comprising a vapor corrosion inhibiting layer on thecoating.
 4. The hub of claim 1, wherein the hub has a thickness of about0.241 millimeters or less.
 5. The hub of claim 1, wherein the coatingcomprises a plating of tin or nickel material.
 6. The hub of claim 5,wherein the plating of tin or nickel material has a thickness of about0.38 micrometers.
 7. The hub of claim 1, wherein the core produces amagnetic force of attraction on the order of about 1,000 grams-force. 8.A hub for a rotating removable data storage device comprising:a) a corecomprising plain carbon steel having about 0.2% or less carbon; and b) acoating on at least a portion of the core, the coating selected from thegroup consisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof, wherein thehub has a thickness of about 0.241 millimeters or less.
 9. The hub ofclaim 8, wherein the coating comprises a plating of tin or nickelmaterial.
 10. The hub of claim 9, wherein the plating of tin or nickelmaterial has a thickness of about 0.38 micrometers.
 11. The hub of claim8, wherein the core produces a magnetic force of attraction on the orderof about 1,000 grams-force.
 12. A hub for a micro-floppy magnetic datastorage disc comprising:a) a core comprising plain carbon steel havingabout 0.2% or less carbon; and b) a coating on at least a portion of thecore.
 13. The hub of claim 12, wherein the coating is selected from thegroup consisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof.
 14. The hubof claim 12, further comprising a vapor corrosion inhibiting layer onthe coating.
 15. The hub of claim 12, wherein the coating comprises aplating of tin or nickel material.
 16. The hub of claim 15, wherein theplating of tin or nickel material has a thickness of about 0.38micrometers.
 17. The hub of claim 12, wherein the core produces amagnetic force of attraction on the order of about 1,000 grams-force.18. A micro-floppy magnetic data storage disc comprising:a) an annularring of magnetic recording media; and b) a hub located within a centralopening in the recording media and secured thereto, the hubcomprising:1) a core comprising plain carbon steel having about 0.2% orless carbon; and 2) a coating on at least a portion of the core.
 19. Thedisc of claim 18, wherein the coating is selected from the groupconsisting of tin, nickel, zinc, chrome, paints, epoxies,epoxy-urethanes, phenolic resins, and combinations thereof.
 20. The discof claim 18, wherein the hub has a thickness of about 0.241 millimetersor less.
 21. The disc of claim 18, further comprising a vapor corrosioninhibiting layer on the coating.
 22. The disc of claim 18, wherein thecoating comprises a plating of tin or nickel material.
 23. The disc ofclaim 18, wherein the core produces a magnetic force of attraction onthe order of about 1,000 grams-force.
 24. A hub for a rotating removabledata storage device comprising:a) a core comprising plain carbon steelhaving about 0.5% or less carbon; b) a primary coating on at least aportion of the core; and c) a vapor corrosion inhibiting layer on theprimary coating.
 25. A hub according to claim 24, wherein the primarycoating comprises a metallic plating.
 26. A hub according to claim 24,wherein the vapor corrosion inhibiting layer comprises an amine.
 27. Thehub of claim 24, wherein the hub has a thickness of about 0.241millimeters or less.
 28. The hub of claim 24, wherein the plain carbonsteel comprises about 0.5% or less carbon.
 29. The hub of claim 24,wherein the plain carbon steel comprises about 0.2% or less carbon. 30.The hub of claim 25, wherein the metallic plating comprises tin ornickel material.
 31. A hub for a micro-floppy magnetic data storage disccomprising:a) a core comprising plain carbon steel having about 0.5% orless carbon b) a primary coating on at least a portion of the core; andc) a vapor corrosion inhibiting layer on the primary coating.
 32. A hubaccording to claim 31, wherein the primary coating comprises a metallicplating.
 33. A hub according to claim 31, wherein the vapor corrosioninhibiting layer comprises an amine.
 34. The hub of claim 32, whereinthe metallic plating comprises tin or nickel material.
 35. The hub ofclaim 31, wherein the core produces a magnetic force of attraction onthe order of about 1,000 grams-force.